Measuring devices incorporating e.g. acceleration sensors and rotation rate sensors supply input variables for electronic systems of modern wheeled vehicles (road motor vehicles, off-road wheeled vehicles and other non-guided wheeled vehicles). Such electronic systems include an anti-lock braking system (ABS), an electronic stability program (ESP), a navigation system, adaptive cruise control (ACC), roll-over protection, systems for stabilizing rolling motions in automobiles and commercial motor vehicles and also in trailers, a control system for controlling airbags, hill-holder systems, light-angle control for headlights, power steering systems, control systems for controlling vehicle suspension and/or damping, systems for controlling force transmission in the powertrain of the vehicle, engine control systems, display systems for indicating the fill level of fuel and other fluids, systems for detecting a vehicle's loading state and/or incorrect tire pressures, door locking systems, anti-theft systems, systems for controlling the vehicle's aerodynamic characteristics, accident data storage systems and detection and/or warning systems for providing indications and/or warnings in the case of severe inclination angles of an off-road vehicle. The invention particularly relates to a combination of the measuring device with at least one of these systems or with any combination of the above systems.
Acceleration sensors in particular supply essential information for the systems mentioned. In many cases the actual (real) longitudinal and/or lateral acceleration of the vehicle is required. On the other hand, acceleration sensors measure, as a function of the orientation of the vehicle, a measured variable that is falsified due to the gravitational force.
DE 196 03 430 A1 describes a circuit arrangement for determining axle loads for a motor vehicle using data supplied by sensors and having a processing circuit for processing said sensor data. In an embodiment of the circuit arrangement, an acceleration signal is corrected by the gravitational component using a gradient measured by a gradient sensor as part of a program to be executed in a control computer.
DE 198 44 913 A1 discloses an apparatus for monitoring a vehicle-mounted lateral acceleration sensor with which a first lateral acceleration variable is acquired. With the aid of determination means, a second lateral acceleration variable is directly determined as a function of wheel speed variables which are acquired using corresponding detection means. To monitor the lateral acceleration sensor, the filtered lateral acceleration variable is compared with the second lateral acceleration variable in monitoring means.
In this description the acceleration variable falsified by gravitational force will be termed the effective acceleration variable. When the vehicle is stationary, the acceleration sensor only measures the effects of gravitational force. The actual acceleration is not therefore present in the measured variable. However, for driving on an inclined surface (inclined in the longitudinal and/or lateral direction) the required actual acceleration is not measured directly. The measured variables available at the output of an acceleration sensor are therefore erroneous. This is all the more disadvantageous in that it is particularly on inclined surfaces that critical driving situations can arise in which the systems to be supplied with the actual acceleration must operate reliably. Similar erroneous measured variables are produced by acceleration sensors disposed in a vehicle body which inclines relative to the chassis during driving e.g. during an acceleration phase of the vehicle (lateral rolling and/or pitching motion in the longitudinal direction of the vehicle). A roll angle of as little as five degrees results in an error of approximately 1 m/s2 in the lateral acceleration of the vehicle.